Organo-amine acid gas adsorption-desorption polymers, proceses for preparing same, and uses thereof

ABSTRACT

An adsorption-desorption material, in particular, crosslinked organo-amine polymeric materials having a weight average molecular weight of from about 500 to about 1×10 6 , a total pore volume of from about 0.2 cubic centimeters per gram (cc/g) to about 2.0 cc/g, and an adsorption capacity of at least about 0.2 millimoles of CO 2  adsorbed per gram of adsorption-desorption material, and linear organo-amine polymeric materials having a weight average molecular weight of from about 160 to about 1×10 6 , a total pore volume of from about 0.2 cubic centimeters per gram (cc/g) to about 2.0 cc/g, and an adsorption capacity of at least about 0.2 millimoles of CO 2  adsorbed per gram of adsorption-desorption material. This disclosure also relates in part to processes for preparing the crosslinked organo-amine materials and linear organo-amine materials. This disclosure further relates in part to the selective removal of CO 2  and/or other acid gases from a gaseous stream containing one or more of these gases using the adsorption-desorption materials.

This application is a divisional application of U.S. application Ser.No. 13/332,500, which claims the benefit of U.S. Provisional ApplicationNo. 61/426,183 filed Dec. 22, 2010.

BACKGROUND

1. Field of the Disclosure

This disclosure relates in part to adsorption-desorption materials, inparticular, to crosslinked organo-amine materials, and linearorgano-amine materials, and to processes for the preparation of thesematerials. This disclosure also relates in part to the use of thesematerials in the selective removal of CO₂ and/or other acid gases from agaseous stream containing one or more of these gases.

2. Discussion of the Background Art

The selective removal of carbon dioxide from mixed gas streams is ofgreat commercial value. Commercially, carbon dioxide may be used forreinjection into gas or liquid hydrocarbon deposits to maintainreservoir pressure and for enhanced product recovery. Due to theadvanced age of many producing reservoirs worldwide and theever-increasing challenge of meeting demand, the expanding use ofenhanced oil recovery (EOR) methods is becoming more widespread.

Typically the source of carbon dioxide for EOR is the producinghydrocarbon stream itself, which may contain anywhere from less than 5%to more than 80% of CO₂.

Additionally, it is desired to capture CO₂ from flue gas of variouscombustion sources, where the stream contains less than about 15% of CO₂and its temperature is relatively high. Yet another need for CO₂ capturetechnology is for the pre-combustion capture of CO₂ from shifted syngasproduced in fuel gasification processes.

Conventional methods for CO₂ capture include cryogenicdistillation/condensation, absorption using liquid solvents, such asamine scrubbing, or sorption using solid sorbents, such as pressureswing adsorption (PSA) and/or temperature swing adsorption (TSA).However, with present technologies, all of these processes require alarge temperature decrease of the gas stream to enable CO₂ condensationor sorption. Conventional methods (PSA, TSA, amine scrubbing) requireCO₂ uptake at relatively low temperatures (e.g., less than 50° C.).Sorbent/solvent regeneration (CO₂ desorption) is accomplished by a stepchange decrease in CO₂ partial pressure (PSA), and/or by a temperatureincrease to above about 100° C. (TSA, amine scrubbing). In all of thesecases, CO₂ capture costs depend significantly on the required heatexchange capacities and energy requirements for gas cooling/heating, thecosts for steam generation for CO₂ desorption, and the high equipmentand energy costs associated with CO₂ recompression.

Conventional amine scrubbing is based on the chemistry of CO₂ withamines to generate carbonate/bicarbonate and carbamate salts.Commercially, amine scrubbing typically involves contacting the CO₂and/or H₂S containing gas stream with an aqueous solution of one or moresimple amines (e.g., monoethanolamine). The process requires high ratesof gas-liquid exchange and the transfer of large liquid inventoriesbetween the absorption and regeneration steps and high energyrequirements for the regeneration of amine solutions. This process ischallenged by the corrosive nature of the amine solutions. Thesechallenges limit the economic viability for large-scale applications(e.g., large combustion sources and power plants) utilizing conventionaltechnologies.

The growing need to incorporate carbon capture and sequestration (CCS)into fossil fuel-based power generation, has triggered acceleratingresearch into alternatives to conventional amine scrubbing technology.Cyclic adsorption technologies (e.g., PSA and TSA) using solidadsorbents are also well-known in the gas purification industry. Theseprocesses avoid many of the limitations of amine scrubbing describedabove, but suffer from a lack of adsorbents having sufficientlyselective CO₂ adsorption under the humid conditions always present incombustion flue gas, as well as the commercial viability of large scaleoperation.

Due to the ever increasing use of CO₂ re-injection for enhanced oilrecovery, technology that reduces the cost of CO₂ capture directlyreduces hydrocarbon production costs. In addition, if anticipated futurerestrictions on CO₂ emissions are mandated, a low cost method for CO₂capture will be a critical need as a part of CCS.

Carbon dioxide is a ubiquitous and inescapable by-product of thecombustion of hydrocarbons. In addition to the use of CO₂ for EOR, thereis growing concern over its accumulation in the atmosphere and its rolein global climate change. Therefore in addition to the commercialbenefits of CO₂ recovery, environmental factors may soon require itscapture and sequestration. For these reasons the separation of CO₂ frommixed gas streams is a rapidly growing area of research.

Therefore, a need exists for developing commercially viable alternativemethods and adsorbent materials for the selective removal of CO₂ fromgas mixtures, particularly adsorption technologies and adsorbentmaterials having economic viability for large-scale (e.g., largecombustion sources and power plants) applications.

SUMMARY OF THE DISCLOSURE

This disclosure relates in part to an acid gas adsorption-desorptionmaterial comprising a crosslinked organo-amine material having a weightaverage molecular weight of from about 500 to about 1×10⁶, a total porevolume of from about 0.2 cubic centimeters per gram (cc/g) to about 2.0cc/g, and an adsorption capacity of at least about 0.2 millimoles of CO₂adsorbed per gram of adsorption-desorption material, or mixturesthereof.

This disclosure also relates in part to an acid gasadsorption-desorption material comprising a linear organo-amine materialhaving a weight average molecular weight of from about 160 to about1×10⁶, a total pore volume of from about 0.2 cubic centimeters per gram(cc/g) to about 2.0 cc/g, and an adsorption capacity of at least about0.2 millimoles of CO₂ adsorbed per gram of adsorption-desorptionmaterial, or mixtures thereof.

This disclosure further relates in part to a process for preparing anacid gas adsorption-desorption material comprising a crosslinkedorgano-amine material having a weight average molecular weight of fromabout 500 to about 1×10⁶, a total pore volume of from about 0.2 cubiccentimeters per gram (cc/g) to about 2.0 cc/g, and an adsorptioncapacity of at least about 0.2 millimoles of CO₂ adsorbed per gram ofadsorption-desorption material, or mixtures thereof; said processcomprising (i) reacting at least one organo halide material comprised ofat least two haloalkyl functional groups, with at least one organo-aminematerial under conditions sufficient to produce an organo-aminematerial, and (ii) crosslinking said organo-amine material underconditions sufficient to produce said crosslinked organo-amine material.

This disclosure yet further relates in part to a process for preparingan acid gas adsorption-desorption material comprising a linearorgano-amine material having a weight average molecular weight of fromabout 160 to about 1×10⁶, a total pore volume of from about 0.2 cubiccentimeters per gram (cc/g) to about 2.0 cc/g, and an adsorptioncapacity of at least about 0.2 millimoles of CO₂ adsorbed per gram ofadsorption-desorption material, or mixtures thereof; the processcomprising reacting at least one organo halide material comprised of atleast two haloalkyl functional groups, with at least one organo-aminematerial under conditions sufficient to produce said linear organo-aminematerial.

This disclosure also relates in part to a method foradsorption-desorption of an acid gas comprising:

contacting a gas mixture containing at least one acid gas with anadsorbent material under conditions sufficient to cause adsorption of atleast a portion of the acid gas, the adsorbent material comprising acrosslinked organo-amine material having a weight average molecularweight of from about 500 to about 1×10⁶, a total pore volume of fromabout 0.2 cubic centimeters per gram (cc/g) to about 2.0 cc/g, and anadsorption capacity of at least about 0.2 millimoles of CO₂ adsorbed pergram of adsorbent material, or mixtures thereof; and

treating the adsorbent material under conditions sufficient to causedesorption of at least a portion of the acid gas.

This disclosure further relates in part to a method foradsorption-desorption of an acid gas comprising:

contacting a gas mixture containing at least one acid gas with anadsorbent material under conditions sufficient to cause adsorption of atleast a portion of the acid gas, the adsorbent material comprising alinear organo-amine material having a weight average molecular weight offrom about 160 to about 1×10⁶, a total pore volume of from about 0.2cubic centimeters per gram (cc/g) to about 2.0 cc/g, and an adsorptioncapacity of at least about 0.2 millimoles of CO₂ adsorbed per gram ofadsorbent material, or mixtures thereof; and

treating the adsorbent material under conditions sufficient to causedesorption of at least a portion of the acid gas.

This disclosure yet further relates in part to a method foradsorption-desorption of carbon dioxide comprising:

contacting a gas mixture containing at least carbon dioxide with anadsorbent material under conditions sufficient to cause adsorption of atleast a portion of the carbon dioxide, the adsorbent material comprisinga crosslinked organo-amine material having a weight average molecularweight of from about 500 to about 1×10⁶, a total pore volume of fromabout 0.2 cubic centimeters per gram (cc/g) to about 2.0 cc/g, and anadsorption capacity of at least about 0.2 millimoles of CO₂ adsorbed pergram of adsorbent material, or mixtures thereof; and

treating the adsorbent material under conditions sufficient to causedesorption of at least a portion of the carbon dioxide.

This disclosure also relates in part to a method foradsorption-desorption of carbon dioxide comprising:

contacting a gas mixture containing at least carbon dioxide with anadsorbent material under conditions sufficient to cause adsorption of atleast a portion of the carbon dioxide, the adsorbent material comprisinga linear organo-amine material having a weight average molecular weightof from about 160 to about 1×10⁶, a total pore volume of from about 0.2cubic centimeters per gram (cc/g) to about 2.0 cc/g, and an adsorptioncapacity of at least about 0.2 millimoles of CO₂ adsorbed per gram ofadsorbent material, or mixtures thereof; and

treating the adsorbent material under conditions sufficient to causedesorption of at least a portion of the carbon dioxide.

This disclosure further relates in part to a method of separating carbondioxide from a gas mixture comprising:

providing at least one adsorption zone comprising an adsorbent, theadsorbent comprising a crosslinked organo-amine material having a weightaverage molecular weight of from about 500 to about 1×10⁶, a total porevolume of from about 0.2 cubic centimeters per gram (cc/g) to about 2.0cc/g, and an adsorption capacity of at least about 0.2 millimoles of CO₂adsorbed per gram of adsorbent material, or mixtures thereof;

passing the gas mixture comprising at least carbon dioxide through theat least one adsorption zone, wherein the adsorbent adsorbs at leastpart of the carbon dioxide from the mixture to provide a carbondioxide-depleted gas; and

regenerating the adsorbent to provide a carbon dioxide-rich gas.

This disclosure yet further relates in part to a method of separatingcarbon dioxide from a gas mixture comprising:

providing at least one adsorption zone comprising an adsorbent, theadsorbent comprising a linear organo-amine material having a weightaverage molecular weight of from about 160 to about 1×10⁶, a total porevolume of from about 0.2 cubic centimeters per gram (cc/g) to about 2.0cc/g, and an adsorption capacity of at least about 0.2 millimoles of CO₂adsorbed per gram of adsorbent material, or mixtures thereof;

passing the gas mixture comprising at least carbon dioxide through theat least one adsorption zone, wherein the adsorbent adsorbs at leastpart of the carbon dioxide from the mixture to provide a carbondioxide-depleted gas; and

regenerating the adsorbent to provide a carbon dioxide-rich gas.

The adsorbent materials useful in this disclosure have the advantage ofrecovery of CO₂ at low pressure, low capital costs, low propensity forcorrosion, and low regeneration energy compared to conventionalprocesses where a large amount of energy is required to heat the aqueousamine solution.

The adsorbent material useful in this disclosure possesses high CO₂uptake capacity at temperatures from about 20° C. to about 160° C. Thisis significantly higher temperatures than where most conventionalsorbents can operate. At these higher temperatures, where conventionalsorbents (e.g., liquid amines, zeolites, and carbons) usually undergoCO₂ desorption, the adsorbent material of this disclosure exhibitssubstantial and quite rapid CO₂ uptake. Complete CO₂ desorption can beaccomplished by a partial pressure swing, wherein the CO₂-containingfeed gas is replaced in the desorption step with an essentially CO₂-freeor low CO₂ content purge gas or fluid under essentially isothermalconditions. Using this CO₂ sorbent material, the need for temperaturecycling is minimized and a rapid cycle partial pressure swing adsorptioncan be carried out at much higher temperature, as well as essentiallyisothermal conditions than practiced with conventional sorbents, therebygreatly reducing the heat exchange cost of CO₂ separation.

As used herein, “essentially isothermal conditions” means at or aboutthe same temperature. In a preferred embodiment, theadsorption-desorption processes of this disclosure are carried out underessentially isothermal conditions.

Further objects, features and advantages of the present disclosure willbe understood by reference to the following drawings and detaileddescription.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 graphically depicts gravimetric uptake of the adsorbent preparedin Example 2.

FIG. 2 graphically depicts diffusion time as a function of particle sizefor the adsorbent used in Example 2.

FIG. 3 shows CO₂ uptake capacity data from a variety ofpolyethyleneimines and aminosilane-modified materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The acid gas adsorption-desorption materials of this disclosure comprisein part crosslinked organo-amine polymeric materials. The crosslinkedorgano-amine materials have a weight average molecular weight of fromabout 500 to about 1×10⁶, preferably a weight average molecular weightof from about 600 to about 1×10⁵, and more preferably a weight averagemolecular weight of from about 1×10³ to about 5×10⁴. The crosslinkedorgano-amine materials have an adsorption capacity of at least about 0.2millimoles of CO₂ adsorbed per gram of adsorption-desorption material,preferably an adsorption capacity of at least about 0.5 millimoles ofCO₂ adsorbed per gram of adsorption-desorption material, and morepreferably an adsorption capacity of at least about 1.0 millimoles ofCO₂ adsorbed per gram of adsorption-desorption material. This disclosurealso includes mixtures of the crosslinked organo-amine materials.

Illustrative crosslinked organo-amine materials of this disclosure havea formula selected from:

[(CH₂CH₂NH)_(x)(R)(NHCH₂CH₂)_(y)]_(n)

wherein x is an integer greater than about 1.0, y is an integer greaterthan about 1.0, n is an integer equal to or greater than about 1.0, theCH₂CH₂NH and NHCH₂CH₂ groups can be linear or branched, and R is thesame or different and is an alkyl or aryl moiety. In a preferredembodiment, at least one R is an aryl moiety. The structure can beterminated with either of the starting monomers as well asmonofunctional amines and monofunctional aryl and/or alkyl halides.

The organo halide and organo-amine monomers can both or independently bedifunctional and/or multifunctional. In cases where both monomers aredifunctional, the product will be a linear organo-amine polymer. Ifeither the organo halide or organo-amine monomers have at least threefunctional groups, the product will be a crosslinked organo-aminepolymer.

As used herein, “crosslinked” means polymer chains that are connected toone another through bonds. Crosslinks are bonds that link one polymerchain to another. When the polymer chains are connected to each other,they lose some of their ability to move as independent polymer chains.

The composition of the crosslinked organo-amine materials of thisdisclosure, including all polymers, copolymers and terpolymers thereof,can vary over a wide range, and need only be that amount necessary toprovide the desired adsorption-desorption properties. These materialscan be formed as bulk solids, films, membranes and particulates.

Preferably, the crosslinked organo-amine polymer materials of thisdisclosure have an average particle diameter of from about 0.1 micronsto about 500 microns, preferably from about 1.0 microns to about 100microns, and more preferably from about 2.0 microns to about 50 microns.Preferably, the crosslinked organo-amine polymer materials of thisdisclosure have a total pore volume of from about 0.2 cubic centimetersper gram (cc/g) to about 2.0 cc/g, preferably from about 0.4 cc/g toabout 2.0 cc/g, and more preferably from about 0.5 cc/g to about 2.0cc/g, as measured by mercury porosimetry in cubic centimeters of porevolume per gram of the porous crosslinked organo-amine materials, forall pores having a diameter of 0.005 microns to 10 microns.

Preferably, the crosslinked organo-amine polymer materials of thisdisclosure have an average pore size of from about 0.01 microns to about1000 microns, preferably from about 0.1 microns to about 100 microns,and more preferably from about 1.0 microns to about 10 microns.Preferably, the crosslinked organo-amine polymer materials of thisdisclosure have a surface area of from about 5 square meters per gram(m²/g) to about 50 m²/g, preferably from about 20 m²/g to about 50 m²/g,and more preferably from about 25 m²/g to about 50 m²/g, as measured bymercury porosimetry.

The crosslinked organo-amine materials of this disclosure can beprepared by a process that involves reacting at least one organo halidematerial with at least one organo-amine material under conditionssufficient to produce the crosslinked organo-amine material. Inparticular, the crosslinked organo-amine materials can be produced byreacting at least one organo halide or mixtures of organo halides, withat least one linear amine, branched amine, polyamine, or mixturesthereof, under conditions sufficient to produce the crosslinkedorgano-amine material.

Illustrative organo halide starting materials useful in making thecrosslinked organo-amine materials of this disclosure may be selectedfrom a wide variety of materials known in the art. Illustrative organohalide starting materials include, for example, benzylic halide andmixtures thereof. Preferably, the organo halide is selected from thegroup consisting of: methylbenzyl chloride, dichloro-p-xylene,crosslinked polystyrene spheres with chemically attachedchloromethylstyrene, and mixtures thereof. Halide starting materialswhich possess at least two haloalkyl functional groups can be preparedby conventional methods known in the art and/or are commerciallyavailable.

Illustrative amine starting materials useful in making the crosslinkedorgano-amine materials of this disclosure may be selected from a widevariety of materials known in the art. Illustrative organo-aminestarting materials include, for example, primary amines, secondaryamines, and mixtures thereof. Suitable polyamines include, for example,linear polyamines, branched polyamines, polyalkyleneimines, and mixturesthereof. Preferably, the organo-amine is selected from propylenediamine,tetraethylenepentaamine, branched and linear polyethyleneimines, andmixtures thereof. The organo-amine starting materials can be prepared byconventional methods known in the art and/or are commercially available.

As indicated above, mixtures of halide starting materials can be used inmaking the crosslinked organo-amine materials of this disclosure. Forexample, one or more aromatic compounds having at least two haloalkylfunctional groups may be used in the halide starting material mixturesin the process of this disclosure. These compounds may be used alone orin combination with the alkyl halide compounds described below.Illustrative aromatic compounds having at least two haloalkyl functionalgroups include, for example,2,4-bis(chloromethyl)-1,3,5-trimethylbenzene,2,4,6-tris-(chloromethyl)-mesitylene,1,3,5-tris-chloromethyl-2,4,6-trimethylbenzene, and mixtures thereof.These aromatic compounds having at least two haloalkyl functional groupscan be prepared by conventional methods known in the art and/or arecommercially available.

One or more alkyl halides may also be used as starting materials in theprocess of this disclosure. These compounds may be used either alone orin combination with the aromatic compounds having at least one haloalkylfunctional group described above. These compounds may be used alone orin combination with the aromatic compounds having at least two haloalkylfunctional groups described above. Illustrative alkyl halides include,for example, polyhalo-alkanes and polyhalo-alkenes having from 1 toabout 12 carbon atoms. The polyhalo-alkanes and polyhalo-alkenes can belinear or branched, and contain two or more halide groups with no limitplaced on their location on the alkane or alkene chain. The alkene chaincan contain one or more carbon-carbon multiple bonds of indeterminatelocation on the chain. Mixtures of alkyl halides are also useful in thisdisclosure. These alkyl halide starting materials can be prepared byconventional methods known in the art and/or are commercially available.

Monofunctional reactants can be incorporated as potential structuredisrupters and/or pore modifiers for functionality control. Anon-limiting example of a monofunctional reactant is methylbenzylchloride.

A wide variation of crosslinkers can be useful in this disclosure.Crosslinker modifications and network functionality can provide enhancedperformance. The crosslinker structure can be varied(tri-/tetra-functional crosslinkers) as well as the crosslink density.Illustrative crosslinkers include, for example,2,4-bis(chloromethyl)-1,3,5-trimethylbenzene,2,4,6-tris-(chloromethyl)-mesitylene,1,3,5-tris-chloromethyl-2,4,6-trimethylbenzene, and mixtures thereof,and the like.

One or more porogens may also be used as a component material in thefabrication processes and crosslinked polymers of this disclosure. Aninterpenetrating network of holes, closed cells or a combination thereofcan be achieved in the crosslinked polymers of this disclosure bypolymerization in the presence of an insoluble material such as aporogen. Subsequent removal of the porogen gives rise to intersticesthroughout the formed crosslinked polymer material. Porogenconcentrations in the range of from about 1.0 weight percent to about 75weight percent, preferably from about 5 weight percent to about 50weight percent, and more preferably from about 10 weight percent toabout 30 weight percent, with respect to the overall reaction mixture,should be sufficient for most processes. Illustrative porogens include,for example, xylene, toluene, polyvinylpyrrolidinone, and mixturesthereof. The porogens can be prepared by conventional methods known inthe art and/or are commercially available.

The concentration of the organo halide starting material in the processof this disclosure can vary over a wide range, and need only be thatminimum amount necessary to react with the organo-amine startingmaterial and to provide the crosslinked organo-amine materials of thisdisclosure. In general, depending on the size of the reaction mixture,organo halide starting material concentrations in the range of fromabout 1.0 weight percent to about 75 weight percent, preferably fromabout 5 weight percent to about 50 weight percent, and more preferablyfrom about 10 weight percent to about 30 weight percent, with respect tothe overall reaction mixture, should be sufficient for most processes.

The concentration of the organo-amine starting material in the processof this disclosure can vary over a wide range, and need only be thatminimum amount necessary to react with the organo halide startingmaterial and to provide the crosslinked organo-amine materials of thisdisclosure. In general, depending on the size of the reaction mixture,organo-amine starting material concentrations in the range of from about1.0 weight percent to about 75 weight percent, preferably from about 5weight percent to about 50 weight percent, and more preferably fromabout 10 weight percent to about 30 weight percent, with respect to theoverall reaction mixture, should be sufficient for most processes.

The concentration of the crosslinkers in the process of this disclosurecan vary over a wide range, and need only be that minimum amountnecessary to achieve desired crosslinking in the crosslinkedorgano-amine materials of this disclosure. In general, depending on thesize of the reaction mixture, concentrations of crosslinkers in therange of from about 0.5 weight percent to about 50 weight percent,preferably from about 1.0 weight percent to about 40 weight percent, andmore preferably from about 2.0 weight percent to about 30 weightpercent, with respect to the overall reaction mixture, should besufficient for most processes.

The concentration of the porogens in the process of this disclosure canvary over a wide range, and need only be that minimum amount necessaryto achieve desired pore volume in the crosslinked organo-amine materialsof this disclosure. In general, depending on the size of the reactionmixture, concentrations of porogens in the range of from about 1.0weight percent to about 75 weight percent, preferably from about 5weight percent to about 50 weight percent, and more preferably fromabout 10 weight percent to about 30 weight percent, with respect to theoverall reaction mixture, should be sufficient for most processes.

Reaction conditions for the reaction of the organo-halide startingmaterial with the organo-amine starting material, such as temperature,pressure and contact time, may vary greatly. Any suitable combination ofsuch conditions may be employed herein that are sufficient to producethe crosslinked organo-amine materials of this disclosure. Preferredreaction pressure is less than about 100 psig. More preferably, thereaction pressure is approximately ambient (atmospheric) pressure.Preferred reaction temperatures can range from about 0° C. to about 150°C., more preferably from about 25° C. to about 95° C. The preferredreaction time of the organo-halide with the organo-amine can range fromabout 60 seconds to about 48 hours. In an embodiment, the reaction iscarried out under ambient pressure and the contact time may vary from amatter of seconds or minutes to a few hours or greater. The reactantscan be added to the reaction mixture or combined in any order. The stirtime employed is preferably from about 1 minute to about 48 hours, morepreferably from about 1 hour to 24 hours, and even more preferably fromabout 2 hours to 8 hours. Isolation of the crosslinked organo-aminematerials may be achieved by any techniques known in the art, such assolvent evaporation or nonsolvent extraction and other conventionalprocedures, to afford the final material.

The acid gas adsorption-desorption materials of this disclosure comprisein part linear organo-amine polymeric materials. Preferably, the linearorgano-amine materials have a weight average molecular weight of fromabout 160 to about 1×10⁶, preferably a weight average molecular weightof from about 400 to about 1×10⁵, and more preferably a weight averagemolecular weight of from about 600 to about 1×10⁴. Preferably, thelinear organo-amine materials have an adsorption capacity of at leastabout 0.2 millimoles of CO₂ adsorbed per gram of adsorption-desorptionmaterial, preferably an adsorption capacity of at least about 0.5millimoles of CO₂ adsorbed per gram of adsorption-desorption material,and more preferably an adsorption capacity of at least about 1.0millimoles of CO₂ adsorbed per gram of adsorption-desorption material.This disclosure also includes mixtures of the linear organo-aminematerials.

Illustrative linear organo-amine materials of this disclosure have aformula selected from:

[(CH₂CH₂NH)_(x)(R)(NHCH₂CH₂)_(y)]_(n)

wherein x is an integer greater than about 1.0, y is an integer greaterthan about 1.0, n is an integer equal to or greater than about 1.0, theCH₂CH₂NH and NHCH₂CH₂ groups can be linear or branched, and R is thesame or different and is an alkyl or aryl moiety. In a preferredembodiment, at least one R is an aryl moiety. The structure can beterminated with either of the starting monomers as well asmonofunctional amines and monofunctional aryl and/or alkyl halides.

The organo halide and organo-amine monomers can both or independently bedifunctional and/or multifunctional. In cases where both monomers aredifunctional, the product will be a linear organo-amine polymer. Ifeither the organo halide or organo-amine monomers have at least threefunctional groups, the product will be a crosslinked organo-aminepolymer.

The composition of the linear organo-amine materials of this disclosure,including all polymers, copolymers and terpolymers thereof, can varyover a wide range, and need only be that amount necessary to provide thedesired adsorption-desorption properties. These materials can be formedas bulk solids, films, membranes and/or particulates.

Preferably, the linear organo-amine polymer materials of this disclosurehave an average particle diameter of from about 0.1 microns to about 500microns, preferably from about 1.0 microns to about 100 microns, andmore preferably from about 2 microns to about 50 microns. Preferably,the linear organo-amine polymer materials of this disclosure have atotal pore volume of from about 0.2 cubic centimeters per gram (cc/g) toabout 2.0 cc/g, preferably from about 0.4 cc/g to about 2.0 cc/g, andmore preferably from about 0.5 cc/g to about 2.0 cc/g, as measured bymercury porosimetry in cubic centimeters of pore volume per gram of theporous crosslinked organo-amine materials, for all pores having adiameter of 0.005 microns to 10 microns.

Preferably, the linear organo-amine polymer materials of this disclosurehave an average pore size of from about 0.01 microns to about 1000microns, preferably from about 0.1 microns to about 100 microns, andmore preferably from about 1.0 microns to about 10 microns. Preferably,the linear organo-amine polymer materials of this disclosure have asurface area of from about 5 square meters per gram (m²/g) to about 50m²/g, preferably from about 20 m²/g to about 50 m²/g, and morepreferably from about 25 m²/g to about 50 m²/g, as measured by mercuryporosimetry.

The linear organo-amine materials of this disclosure can be prepared bya process that involves reacting at least one organo halide materialwith at least one organo-amine material under conditions sufficient toproduce the linear organo-amine material. In particular, the linearorgano-amine materials can be produced by reacting at least one organohalide or mixtures of organo halides, with at least one linear amine, ormixtures thereof, under conditions sufficient to produce the linearorgano-amine material.

Illustrative organo halide starting materials useful in making thelinear organo-amine materials of this disclosure may be selected from awide variety of materials known in the art. Illustrative organo halidestarting materials include, for example, benzylic halide and mixturesthereof. Preferably, the organo halide is selected from methylbenzylchloride, dichloro-p-xylene, crosslinked polystyrene spheres withchemically attached chloromethylstyrene, and mixtures thereof. Theorgano halide materials can be prepared by conventional methods known inthe art and/or are commercially available.

Illustrative organo-amine starting materials useful in making the linearorgano-amine materials of this disclosure may be selected from a widevariety of materials known in the art. Illustrative organo-aminestarting materials include, for example, primary amines, secondaryamines, and mixtures thereof. Suitable polyamines include, for example,linear polyamines, linear polyalkyleneimines, and mixtures thereof.Preferably, the organo-amine is selected from propylenediamine,tetraethylenepentaamine, linear polyethyleneimines, and mixturesthereof. The organo-amine materials can be prepared by conventionalmethods known in the art and/or are commercially available

As indicated above, mixtures of organo halide starting materials can beused in making the linear organo-amine materials of this disclosure. Forexample, one or more aromatic compounds having at least two haloalkylfunctional groups may be used in the halide starting material mixturesin the process of this disclosure. These compounds may be used alone orin combination with the alkyl halide compounds described below.Illustrative aromatic compounds having at least two haloalkyl functionalgroups include, for example,2,4-bis(chloromethyl)-1,3,5-trimethylbenzene,2,4,6-tris-(chloromethyl)-mesitylene,1,3,5-tris-chloromethyl-2,4,6-trimethylbenzene, and mixtures thereof.These aromatic compounds having at least two haloalkyl functional groupscan be prepared by conventional methods known in the art and/or arecommercially available.

One or more alkyl halides may also be used as starting materials in theprocess of this disclosure. These compounds may be used alone or incombination with the aromatic (or “arene” or “aryl”) compounds having atleast two haloalkyl functional groups described above. Illustrativealkyl halides include, for example, polyhalo-alkanes andpolyhalo-alkenes having from 1 to about 12 carbon atoms. Thepolyhalo-alkanes and polyhalo-alkenes can be linear or branched, andcontain two or more halide groups with no limit placed on their locationon the alkane or alkene chain. The alkene chain can contain one or morecarbon-carbon multiple bonds of indeterminate location on the chain.Mixtures of alkyl halides are also useful in this disclosure. Thesealkyl halide starting materials can be prepared by conventional methodsknown in the art and/or are commercially available.

One or more porogens may also be used as a component material in thefabrication processes and linear polymers of this disclosure. Aninterpenetrating network of holes, closed cells or a combination thereofcan be achieved in the linear polymers of this disclosure bypolymerization in the presence of an insoluble material such as aporogen. Subsequent removal of the porogen gives rise to intersticesthroughout the formed linear polymer material. Porogen concentrations inthe range of from about 1.0 weight percent to about 75 weight percent,preferably from about 5 weight percent to about 50 weight percent, andmore preferably from about 10 weight percent to about 30 weight percent,with respect to the overall reaction mixture, should be sufficient formost processes.

Illustrative porogens include, for example, xylene, toluene,polyvinylpyrrolidinone, and mixtures thereof. The porogens can beprepared by conventional methods known in the art and/or arecommercially available.

The concentration of the organo halide starting material in the processof this disclosure can vary over a wide range, and need only be thatminimum amount necessary to react with the amine starting material andto provide the linear organo-amine materials of this disclosure. Ingeneral, depending on the size of the reaction mixture, organo halidestarting material concentrations in the range of from about 1.0 weightpercent to about 75 weight percent, preferably from about 5 weightpercent to about 50 weight percent, and more preferably from about 10weight percent to about 30 weight percent, with respect to the overallreaction mixture, should be sufficient for most processes.

The concentration of the organo-amine starting material in the processof this disclosure can vary over a wide range, and need only be thatminimum amount necessary to react with the organo halide startingmaterial and to provide the linear organo-amine materials of thisdisclosure. In general, depending on the size of the reaction mixture,organo-amine starting material concentrations in the range of from about1.0 weight percent to about 75 weight percent, preferably from about 5weight percent to about 50 weight percent, and more preferably fromabout 10 weight percent to about 30 weight percent, with respect to theoverall reaction mixture, should be sufficient for most processes.

The concentration of the porogens in the process of this disclosure canvary over a wide range, and need only be that minimum amount necessaryto achieve desired pore volume in the linear organo-amine materials ofthis disclosure. In general, depending on the size of the reactionmixture, concentrations of porogens in the range of from about 1.0weight percent to about 75 weight percent, preferably from about 5weight percent to about 50 weight percent, and more preferably fromabout 10 weight percent to about 30 weight percent, with respect to theoverall reaction mixture, should be sufficient for most processes.

Reaction conditions for the reaction of the organo halide startingmaterial with the amine starting material, such as temperature, pressureand contact time, may vary greatly. Any suitable combination of suchconditions may be employed herein that are sufficient to produce thelinear organo-amine materials of this disclosure. Preferred reactionpressure is less than about 100 psig. More preferably, the reactionpressure is approximately ambient (atmospheric) pressure. Preferredreaction temperatures can range from about 0° C. to about 150° C., morepreferably from about 25° C. to about 95° C. The preferred reaction timeof the organo halide with the organo-amine can range from about 60seconds to about 48 hours. In an embodiment, the reaction is carried outunder ambient pressure and the contact time may vary from a matter ofseconds or minutes to a few hours or greater. The reactants can be addedto the reaction mixture or combined in any order. The stir time employedis preferably from about 1 minute to about 48 hours, more preferablyfrom about 1 hour to 24 hours, and even more preferably from about 2hours to 8 hours. Isolation of the linear organo-amine materials may beachieved by any techniques known in the art, such as solventevaporation, nonsolvent extraction and other conventional methods, toafford the final material.

The method of this disclosure involves removing CO₂ and/or other acidgases, such as H₂S, from a gaseous stream containing one or more ofthese gases. The method of this disclosure is based on the selectiveadsorption of a gas mixture and involves contacting the gas mixture witha selective adsorbent in an adsorption zone. The adsorption zone ismaintained at adsorption conditions (i.e., temperature and/or pressure)favorable to selectively adsorbing a component of the gas mixture andproducing an adsorption effluent, which has reduced concentration of theadsorbed component relative to the gas mixture. Subsequently, theadsorbed component is then desorbed by changing the conditions in theadsorption zone to induce desorption. Alternatively, the selectiveadsorbent can be moved from the adsorption zone to a desorption zonehaving conditions favorable for desorption. Under desorption conditions,at least a portion of the adsorbed component is desorbed from theselective adsorbent. Following the desorptive step, the adsorption zonemay be further purged with a purge gas to further remove the adsorbedcomponent.

Once the adsorbent has been synthesized, it can be employed in a sorbentbed for use the adsorption-desorption process. Preferably, the adsorbentof this disclosure should be formed into a stable, mechanically strongform. These forms may include, for example, pellet forms or monolithicstructures. The selection of the appropriate form is based on theapplication of the adsorbent and the type of equipment used. After theadsorbent form is selected and manufactured, it is used in a sorbent bedwhere a gaseous stream containing CO₂ contacts the adsorbent. In theadsorption process, the CO₂ and amine chemically react to form an aminecomplex, thereby removing the CO₂ from the gaseous stream.

After the adsorbent is loaded with CO₂ to a satisfactory level, forexample, when greater than 80 percent of the amine has been converted tothe amine complex, or at a designated cycle time, the adsorbent can beregenerated. Regeneration involves ceasing the flow of the gaseousstream through the bed and desorbing the adsorbed CO₂. The desorptioncan be accomplished by controlled temperature swing, pressure swing,partial pressure swing, or by the use of a sweeping or purge gas, or anycombination thereof. During this step, the amine complex is dissociated,and CO₂ removed and the amine is freed and ready for re-use. In anembodiment, the adsorption-desorption can be carried out underessentially isothermal conditions.

The adsorbent material of this disclosure comprises a crosslinkedorgano-amine material or a linear organo-amine material. Suitablecrosslinked organo-amine materials and linear organo-amine materials ofthis disclosure are described more fully herein.

The adsorbent material has an adsorption capacity of at least about 0.2millimoles, preferably at least about 0.5 millimoles, and morepreferably at least about 1.0 millimoles, of CO₂ adsorbed per gram ofadsorbent when measured by a thermal gravimetric apparatus using a drygas stream containing CO₂ (about 0.7 atmosphere partial pressure) and aninert gas. The adsorbent can be regenerated from one cycle to another incycling adsorption processes, and thus the adsorbent is cyclicallystable.

The adsorption beds can be configured in a variety of ways, for example,moving beds and fixed beds. The configuration is preferably fixed bedwherein the fixed bed is fixed relative to the flow of the feedstreamthrough the bed. In a moving bed configuration, the adsorbent in theadsorption bed and the gas mixture move through the adsorption zone in acontinuous manner. Then the adsorbent is moved from the adsorption zoneinto the desorption zone.

In the preferred fixed bed configuration, the bed is fixed in a certainarea of the cyclic adsorption apparatus and contains the adsorbent. Thegas mixture passes through the fixed bed while under adsorption zoneconditions. After a period of time when the adsorbent adsorbs a portionof the gas mixture, the conditions are changed in the area that includesthe fixed bed to desorption zone conditions to desorb the adsorbedgases. Many cyclic adsorption apparatus configurations can include twoor more fixed beds in separate regions or the apparatus, so that whileone fixed bed is under adsorption conditions, the other fixed bed isunder desorption conditions. Therefore, the gas stream can be operatedin a continuous manner.

In general, for temperature swing adsorption processes, the temperaturein the adsorption zone is lower than the temperature in the desorptionzone, while the pressure is substantially constant. For pressure swingadsorption processes, the pressure in the adsorption zone is greaterthan the pressure of the desorption zone, while the temperature issubstantially constant.

The temperature of the adsorption zone for cyclic adsorption processesdepends upon a number of factors, such as the particular hydrocarbonspresent in the gas mixture being separated, the particular adsorbentbeing used, and the pressure at which the adsorption step is carriedout. The upper and lower temperatures at which the adsorption zone ismaintained is, in part, determined by both economics and the chemicalreactivity of the components in the gas mixture. In particular, thetemperature at which the adsorption zone is maintained should be belowthe temperature at which the gas mixture components undergo chemicalreaction (e.g., hydrocarbons undergoing oligomerization andpolymerization).

For the adsorption processes of this disclosure, the temperature of theinlet stream is preferably in the range of from about 20° C. to about150° C., more preferably from about 75° C. to about 125° C., and evenmore preferably greater than about 80° C. In a preferred embodiment, theadsorption-desorption is carried out under essentially isothermalconditions. The pressure during adsorption is preferably in the range offrom about 0.1 bar to about 300 bar (absolute), more preferably fromabout 0.1 bar to about 150 bar (absolute). The partial pressure ofcarbon dioxide in the gas mixture is preferably from about 0.1 to about150 bar, more preferably from about 0.1 to about 20 bar, and even morepreferably from about 0.1 to about 10 bar (absolute). The gas mixturecan be contacted with the adsorbent bed material at a gas hourly spacevelocity (GHSV) of from about 200 to about 50,000 GHSV. The gas mixturecan be contacted with the adsorbent material in the processes of thisdisclosure one or more times.

The carbon dioxide can be desorbed from the adsorbent material by anyconventional methods. One possibility is to desorb the carbon dioxide bymeans of a helium purge. Other possibilities include pressure swingadsorption including partial pressure swing adsorption, thermal swingadsorption, rapid cycle partial pressure swing to adsorption, or anycombination thereof.

For desorption, suitable pressures can range from preferably about 50millibar to about 75 bar (absolute), more preferably from about 50millibar to about 3 bar (absolute), even more preferably from about 100millibar to about 1.5 bar (absolute). The temperature is preferably inthe range of from about 50° C. to about 150° C., more preferably fromabout 75° C. to about 125° C., and even more preferably greater thanabout 80° C. In a preferred embodiment, the adsorption-desorption iscarried out under essentially isothermal conditions.

For temperature swing adsorption processes, adsorbent regeneration iscarried out at a temperature higher than the adsorption temperature andbelow the temperature at which undesired reactions of the components ofthe gas mixture take place. For temperature swing adsorption processes,the adsorbent regeneration temperature is typically in the range ofabout 40° C. to less than about 200° C., preferably from about 60° C. toabout 140° C. The pressures at which the adsorption and adsorbentregeneration steps are carried out are not critical for temperatureswing adsorption processes, and in general these steps can be carriedout at any of the usual pressures employed for cyclic adsorptionprocesses.

It is understood that the adsorbent is not limited to use for theremoval of CO₂ from a gaseous stream. Rather the adsorbent can be usedfor the removal of any acid gas, or combination thereof, from a gaseousstream, provided that the acid gas is capable of reaction with amines.

The gas mixture containing carbon dioxide can originate from a naturalor artificial source. The gas mixture can contain in addition to carbondioxide, one or more other gases such as methane, ethane, n-butane,i-butane, hydrogen, carbon monoxide, ethene, ethyne, propene, nitrogen,oxygen, helium, neon, argon, krypton, and hydrogen sulfide.

The constituents of the gas mixture may have different proportions. Theamount of carbon dioxide in the gas mixture is preferably at least 1percent by volume, more preferably at least 10 percent by volume, andeven more preferably 50 percent by volume or greater. The gas mixturecan be any of a variety of gases, for example, natural gas, flue gas,fuel gas, waste gas and air.

The contacting of the gas mixture can be carried out by continuousadsorption on a fixed bed. The gas mixture is passed through the fixedadsorbent bed. Continuous adsorption can take place in two or moreadsorbent beds in which at least one of the adsorbent beds contains thecrosslinked organo-amine material or linear organo-amine material or acombination thereof.

The gas mixture can be subject to dehumidification prior to contactingwith the adsorbent material. The dehumidification can be carried out byconventional methods. For example, the dehumidification can be carriedout by adsorption over fixed bed reactors containing solid sorbents.Preferred solid sorbents include, for example, molecular sieves, silicagels or aluminas.

It will be appreciated that conventional equipment can be used toperform the various functions of the cyclic processes, such asmonitoring and automatically regulating the flow of gases within thecyclic adsorption system so that it can be fully automated to runcontinuously in an efficient manner.

Various modifications and variations of this disclosure will be obviousto a worker skilled in the art and it is to be understood that suchmodifications and variations are to be included within the purview ofthis application and the spirit and scope of the claims.

EXAMPLE 1

The reaction of α,α′-dichloro-p-xylene (DCX) withtetraethylenepentaamine (TEPA) produces an essentially linear polymericstructure, while the reaction of DCX with a polyethyleneimine produces achemically crosslinked structure. The level of crosslinking is directlyrelated to the initial stoichiometry ratio of DCX, TEPA and thepolyethyleneimine, and mixtures thereof, as well as the reactiontemperature. At high levels of TEPA addition, the product will containboth chemical crosslinks and pendant (i.e., branched) TEPA moieties. Athigh levels of polyethyleneimine addition, the product will contain bothchemical crosslinks and pendant (i.e., branched) polyethyleneiminemoieties.

The reaction of benzylic halides with primary amines produces secondaryamines, and the reaction of benzylic halides with secondary aminesproduces tertiary amines. Low temperatures can be used to facilitate theformation of secondary amines. High temperatures can be used tofacilitate the formation of linear and branched structures, i.e., theformation of secondary and tertiary amines.

EXAMPLE 2

0.75 grams of DCX was dissolved in dry 48.5 milliliters of toluene whilepurging with nitrogen gas. Agitation was provided with a mechanicalstirrer. Subsequently, 3.62 grams of a polyethyleneimine (number averagemolecular weight 423) was added dropwise into the toluene solution. Atall times, the synthesis was performed at room temperature. Initially,the solution was optically clear. However, as the reaction proceeded,the solution began to turn cloudy. Within a few hours an “oil-like”material appeared in the flask. After several days had elapsed, thesolvent was evaporated by application of a vacuum. 50 milliliters ofacetone was added with continual stirring for 30 minutes. The resultantsolid material was separated by centrifugation. Finally, a 2% solutionof NaOH/methanol (50 milliliters) was added with continual stirring. Thewhite precipitate was collected, washed with deionized water and dried.This material was used in the subsequent absorption measurementspresented in the following examples.

EXAMPLE 3

1.5 grams of DCX (8.58 mmoles) was dissolved in toluene (48.5milliliters). Subsequently, 1.62 grams of TEPA (8.58 mmoles) was addedto the solution in a dropwise fashion. After about 20 minutes, theinitially clear solution began to turn cloudy. The solution was agitatedat room temperature for approximately 12 hours. The solid material wasisolated, neutralized and dried as in the previous examples. NMRanalysis is consistent with the anticipated structure for a difunctionalmonomer capable of being chemically crosslinked.

EXAMPLE 4

CO₂ absorption data as a function of temperature and pressure is shownin FIG. 1 for the adsorbent of Example 2. The graph shows that thisadsorbent material is highly effective in absorbing carbon dioxide fromthe feed stream. The desorption process is also effective at highertemperatures.

EXAMPLE 5

Diffusion time as a function of particle size is show in FIG. 2 for theadsorbent of Example 2. Decreased particle size provides higher surfacearea for absorption to occur. Absorption kinetics were also enhanced.

EXAMPLE 6

FIG. 3 shows data from a variety of polyethyleneimine andaminosilane-modified materials. With the exception of an aqueoussolution of pure polyethyleneimine, the adsorbent material of thisdisclosure (i.e., DCX-Polyethyleneimine 423) exhibits superior CO₂uptake capacity than all of the comparative materials tested at asubstantially higher temperature. Note that the closest capacitymaterial (GT-HAS) suffers considerable capacity loss at an adsorptiontemperature of 75° C. The data for AP-SBA, Diamine-SBA,Polyethyleneimine-SBA, TEPA-SBA and GT-HAS was collected in humidifiedCO₂. The sorbents listed in FIG. 3 are identified as follows:Polyethyleneimine 423/SiO₂=polyethyleneimine with average molecularweight of 423 impregnated into amorphous silica;AP-SBA=aminopropylsilane modified mesoporous silica;Diamine-SBA=2-aminoethyl-aminopropylsilane modified mesoporous silica;Polyethyleneimine 423/SBA (olig.)=polyethyleneimine with averagemolecular weight of 423 impregnated into mesoporous silica;Polyethyleneimine/SBA (750K)=polyethyleneimine with average molecularweight of 750,000 impregnated into mesoporous silica;TEPA-SBA=tetraethylenepentamine impregnated mesoporous silica;GT-HAS=hyperbranched aminosilica material available from Georgia Tech,Atlanta, Ga.; DCX (dichloroxylene)-Polyethyleneimine 423=copolymer ofdichloroxylene-polyethyleneimine prepared according to Example 2; andPure Polyethyleneimine=15 percent aqueous solution (molecular weight of433).

While we have shown and described several embodiments in accordance withour disclosure, it is to be clearly understood that the same may besusceptible to numerous changes apparent to one skilled in the art.Therefore, we do not wish to be limited to the details shown anddescribed but intend to show all changes and modifications that comewithin the scope of the appended claims.

What is claimed is:
 1. A process for preparing an acid gasadsorption-desorption material comprising a linear organo-amine materialhaving a weight average molecular weight of from about 160 to about1×10⁶, a total pore volume of from about 0.2 cubic centimeters per gram(cc/g) to about 2.0 cc/g, and an adsorption capacity of at least about0.2 millimoles of CO₂ adsorbed per gram of adsorption-desorptionmaterial, or mixtures thereof; said process comprising reacting at leastone organo halide material comprised of at least two haloalkylfunctional groups, with at least one organo-amine material underconditions sufficient to produce said linear organo-amine material. 2.The process of claim 1 which is carried out in the presence of at leastone porogen.
 3. The process of claim 2 wherein said at least one porogenis selected from the group consisting of: xylene, toluene andpolyvinylpyrrolidinone.